The goals of the experiments to be carried out under this proposal are (1) to collect high resolution native x-ray intensity data sets to aid in the structure determination and refinement of the Staphlococcus aureus SarA (staphylococcal accessory regulator) protein and the lambda repressor cI-OR1/OR2 complex and (2) to extend the resolution of the structures of the ligand binding domain of the bacterial multidrug resistance regulator, BmrR, the Purine repressor-corepressor-purF operator complex and the CREBDNA-binding domain (bZIP)-CRE complex, which have been solved to 2.7 E, 2.5 E and 3.3 E resolution, respectively.